Tier 1 payments are based on 1314 running hours of the renewable heating system, so a quick calculation would be to multiply the power capacity of the system by 1314.
Assuming a 90kW Ground Source Heat Pump is installed:
Therefore 1314 x 90kW = 118,260 kWh
118,260kWh x tariff = 118,260 x £0.0895 = £10,584 per annual (index linked)
Without calculating interest rates over 20 years you would receive £211,685
Note: If and when a heating system runs over 1314 hours in one year then you still receive tier 2 tariff.
Tariffs that apply for installations with an accreditation date on or after 1 April 2016: